Once again, scientists have exerted a great deal of time and effort to prove something you've probably noticed on your own: Much like shakable body parts, you may have gotten your tendency to be thin or fat from your momma.

According to EurekAlert, University of London researchers found thin parents tend to have thin children after analyzing data from an annual survey of households in England. From 2001 to 2006 researchers collected height and weight information from 7,000 families, then calculated their BMI. They concluded that there's a strong association between the body sizes of the two generations. The study found:

When both parents were in the thinner half of the healthy-weight range, the chance of the child being thin was 16.2%, compared with 7.8% when both parents were in the upper half of the healthy weight range, 5.3% with two overweight parents, and only 2.5% for children with two obese parents.

The researchers didn't find that either parent's weight had more of an influence on their child. Other studies have found that the children of obese parents are more likely to be overweight, but it's unusual for a study to focus on the other side of the spectrum. Professor Jane Wardle, UCL Epidemiology & Public Health, explained the science behind the phenomenon:

"Parents are often concerned if their child is thin, but it may just be their 'skinny genes'. All genes have two versions, called alleles. We might think of weight-related genes as having a 'skinny' and 'curvy' allele. Thinner parents are likely to have more of the skinny alleles, increasing the chance of passing them on to their children. A child who inherits more of the skinny alleles from their parents will be naturally thinner."

One obvious question is whether a genetic predisposition to be thinner or heavier has more bearing on a child's weight than behaviors passed on from parents to children. However, Wardle tells NPR,

"Asking this question sets up a false dichotomy ... The way the weight-related genes work, is that they tend to give you either a big appetite or a small appetite."

Of course, genetics isn't the final say on what someone's body size will be. The study may actually highlight how little we do understand about the science of weight. If we're still working on proving that weight-related genes are hereditary, we have a long way to go before we'll know how to control what they do.